The present invention relates to a light emitting device. More specifically, the present invention relates to an organic electroluminescence light emitting device.
In recent years, attention has been paid to an organic electroluminescence display apparatus (hereinafter sometimes abbreviated simply as “organic EL display apparatus”) using an organic electroluminescence device (hereinafter sometimes abbreviated simply as “organic EL device”) as a display apparatus which is a replacement for a liquid crystal display apparatus. The organic EL display apparatus is a self-luminous type and has such a characteristic that a consumed electrical power is low, and it is considered to have sufficient responsiveness to high-speed video signals with a high definition. Its development and commercialization toward practical implementation are being extensively advanced.
In general, the organic EL device has a structure in which a first electrode, an organic layer having a light emitting layer made of an organic light emitting material provided therein and a second electrode are successively laminated. In the organic EL device, it is attempted to control light emitted in the light emitting layer through an enhancement of color purity of luminous color or an increase of luminous efficiency or the like by introducing a resonator structure, namely, by contriving to optimize a thickness of each of layers constituting the organic layer (see, for example, WO 01/39554).
Here, there may be the case where a problem is caused in viewing angle dependency of chromaticity or luminance, namely, there may be the case where a problem that as a viewing angle becomes large, a peak wavelength in a spectrum of light from an organic EL display apparatus largely moves, or light intensity is greatly lowered is caused; and therefore, it is desirable that the intensity of resonance is suppressed to a lower level as far as possible, namely, the thickness of the organic layer is made thin as far as possible (see, for example, the above-cited WO 01/39554). However, in the case where the thickness of the organic layer is thin, as schematically shown in FIG. 14, when a particle (foreign matter) or a protruding part is present on the first electrode, coverage of the organic layer does not become complete so that there is a concern that a short circuit is caused between the first electrode and the second electrode. Then, when such a short circuit is caused, in an organic EL display apparatus of an active matrix system, a pixel including the short circuit becomes a defect, thereby deteriorating the display quality of the organic EL display apparatus. Also, in an organic EL display apparatus of a passive matrix system, such a pixel including the short circuit becomes a missing line, thereby deteriorating the display quality of the organic EL display apparatus, too. Such a problem becomes a remarkable problem especially in a large-sized organic EL display apparatus. That is, this is because the viewing angle characteristic becomes severer, whereby a tolerable number of defects per unit area becomes small.
Up to date, grappling with decreasing the short circuit between the first electrode and the second electrode has been made in all sorts of ways. For example, JP-A-2001-035667 discloses a technology in which in an organic EL display apparatus of a bottom emission system, a highly resistive layer is inserted between an anode electrode and an organic film. Also, JP-A-2006-338916 discloses a technology in which in an organic EL display apparatus of a top emission system, an anode electrode is divided into two layers, and the layer constituting the anode electrode close to an organic layer is made highly resistive. Furthermore, JP-A-2005-209647 discloses a technology in which in an organic EL display apparatus of a bottom emission system, a cathode electrode is divided into two layers, and the layer constituting the cathode electrode close to an organic layer is made highly resistive.